Load limiting structure for vehicle occupant restraint system

ABSTRACT

A new and useful load-limiting device for a vehicle occupant restraint is provided. The load-limiting device comprises a mechanical structure designed to dissipate forces applied by a vehicle occupant to the load-limiting device during a crash, to absorb energy applied to a vehicle occupant during a crash. Moreover, the design of the load-limiting device of the present invention provides significant flexibility in designing the predetermined manner in which the load-limiting device dissipates forces during a crash, thereby providing flexibility in how energy of a vehicle occupant is absorbed during a crash. In its basic form, the load limiting device comprises a housing and a deformable member, at least one of which is configured for connection to a vehicle safety belt and the other of which is configured for connection to an anchor point (e.g. a structural part of a vehicle). The housing and the deformable member are moveable relative to each other in a predetermined manner when force is applied to the one of those members, and the housing supports a hardened member formed of a material which is harder than the deformable member and which is positioned to engage and deform the deformable member as the deformable member is being moved relative to the housing. The configuration of the deformable member can be designed so that the deformable member will deform in a predetermined manner under forces applied to the load-limiting device by a vehicle occupant during a crash.

FIELD OF THE INVENTION

The present invention relates to a load limiting structure for a vehicleoccupant restraint.

BACKGROUND OF THE INVENTION

A typical vehicle occupant restraint system for a vehicle comprises abelt system (often comprising a lap belt portion and a shoulder beltportion) anchored to structural parts of the vehicle such as the floor,a pillar such as a B pillar or to a seat frame. Where the restraintsystem includes a shoulder belt portion (also referred to herein as a“shoulder harness”), the shoulder harness typically extends through aweb guide that is coupled to a structural part of the vehicle such asthe B pillar or the seat frame. The restraint system further includes aretractor, often called an “ELR” or emergency locking retractor, whichis designed to take up or provide a controlled amount of slack in thebelt system when the belt system has been fitted about a vehicleoccupant. The retractor allows payout of belt (typically the shoulderbelt) in response to movement of the vehicle occupant during normalvehicle operation. However, at the onset of a crash, the retractorbecomes automatically locked, to restrain further belt payout, and tokeep the vehicle occupant in her or his seat.

The prior art also teaches vehicle occupant restraint systems withtensioning devices, also referred to as “belt tighteners”, and/orload-limiting devices, to better control the manner in which force(s)are applied to a vehicle occupant during a crash. Specifically, atensioning device applies a positive force to the belt immediately atthe onset of a crash, to tighten the restraint against the vehicleoccupant. A load-limiting device acts between the belt or retractor anda structural part of the vehicle and dissipates force applied to avehicle occupant during a crash. When a tensioning device/belt tightenerand load-limiting device are combined into a vehicle occupant restraintsystem, the tensioning device reduces residual slack in the seat beltsystem and the load-limiting device controls the subsequent dissipationof force on a vehicle occupant during the crash.

U.S. Pat. Nos. 6,183,015 B1, 6,196,589 B1 and 6,209,916 B1 teach knowntypes of load limiting devices. In those patents a load limiting deviceincludes a hydraulic piston with fluid chambers on its opposite sides,and a flow control system for controlling flow to one or both chambers,to control movement of the piston under forces applied to the piston bya vehicle occupant restraint system. Moreover, in those patents a crushtube is provided, and is crushed by the piston as the piston moves inone direction in the fluid chamber, to further dissipate forces appliedto the piston by a vehicle occupant restraint system.

SUMMARY OF THE INVENTION

The present invention provides a new and useful concept for aload-limiting device for a vehicle occupant restraint system. Theload-limiting device comprises a mechanical structure designed todissipate forces applied to the load-limiting device in a predeterminedmanner during a vehicle crash, to absorb (take up) force applied to avehicle occupant during a vehicle crash. Moreover, the design of theload-limiting device of the present invention provides significantflexibility in designing the predetermined manner in which theload-limiting device dissipates forces during a vehicle crash, therebyproviding flexibility in how force applied to a vehicle occupant isabsorbed during a crash.

According to the present invention, a load limiting device comprises ahousing and a deformable member, at least one of which is configured forconnection to a component of a vehicle safety restraint and the other ofwhich is configured for connection to a structural part of a vehicle,also referred to herein as an anchor point. The housing and thedeformable member are moveable relative to each other in a predeterminedmanner when force is applied to the one of these members. The housingsupports a hardened member formed of a material that is harder than thedeformable member and which is positioned to engage and deform thedeformable member as the deformable member is being moved relative tothe housing.

The configuration of the deformable member can be designed so that thedeformable member will deform in a predetermined manner under forcesapplied to the load-limiting device during a crash. For example,according to one embodiment, the deformable member is configured todeform in a predetermined digressive force manner as the deformablemember is being moved relative to the housing. In another embodiment,the deformable member is configured to deform in a relatively constantforce manner as the deformable member is being moved relative to thehousing. In yet another embodiment, the deformable member is configuredto deform in a predetermined progressive force manner as the deformablemember is being moved relative to the housing. In yet anotherembodiment, the deformable member is configured to deform in adigressive step manner as the deformable member is being moved relativeto the housing.

These and other features of the present invention will become furtherapparent from the following detailed description and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a vehicle occupant restraint system with aload-limiting device formed according to the principles of the presentinvention.

FIG. 2 is a perspective view of a load-limiting device according to oneembodiment of the present invention.

FIG. 3 is an exploded view of the load-limiting device of FIG. 2.

FIG. 4 is a top view of the load limiting device of FIG. 2.

FIGS. 5 and 6 are cross sectional views of the load limiting device ofFIG. 4, taken from the directions 5-5 and 6-6, respectively.

FIG. 7 schematically illustrates a digressive force/displacement curve,to illustrate the digressive manner in which a vehicle occupantrestraint with a deformable metal strip of FIGS. 2-6 is configured todissipate forces as the strip is being pulled through the housing.

FIG. 8 is a top view of a load-limiting device comprising a deformablemetal strip configured to deform in a predetermined relatively constantforce manner as the strip is being pulled through the housing, inaccordance with another embodiment of the present invention.

FIG. 9 is a top view of another form of load-limiting device comprisinga deformable metal strip configured to deform in a predeterminedrelatively constant force manner as the strip is being pulled throughthe housing, in accordance with another embodiment of the presentinvention.

FIG. 10 schematically illustrates a relatively constantforce/displacement curve, to illustrate the constant force manner inwhich a vehicle occupant restraint with the deformable metal strip ofFIG. 8 or 9 is configured to dissipate forces as the strip is beingpulled through the housing.

FIG. 11 schematically illustrates a load-limiting device comprising adeformable metal strip configured to deform in a predeterminedprogressive force manner as the strip is being pulled through thehousing, in accordance with yet another embodiment of the presentinvention.

FIG. 12 schematically illustrates a progressive force/displacementcurve, to illustrate the digressive manner in which a vehicle occupantrestraint with the deformable metal strip of FIG. 11 is configured todissipate forces as the strip is being pulled through the housing.

FIG. 13 schematically illustrates a load-limiting device comprising adeformable metal strip configured to deform in a predetermineddigressive step force manner as the strip is being pulled through thehousing, in accordance with another embodiment of the present invention.

FIG. 14 schematically illustrates a digressive step force/displacementcurve, to illustrate the digressive manner in which a vehicle occupantrestraint with the deformable metal strip of FIG. 13 is configured todissipate forces as the strip is being pulled through the housing.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a load-limiting device for a vehicleoccupant restraint, which dissipates forces applied to the vehicleoccupant restraint in a predetermined manner during a crash. Theprinciples of the present invention are applicable to differentconfigurations for a vehicle occupant restraint, and are described belowin connection with a belt system that includes a lap belt and shoulderharness (which is often referred to as a three-point safety restraintsystem). It will be clear to those in the art the principles of theinvention are applicable to a variety of vehicle occupant restraints(e.g. front and rear seat belts, etc) and are applicable to vehicleoccupant restraints anchored directly to a structural part of a vehicle(e.g. a vehicle floor, B-pillar, etc.) and to vehicle restraintsanchored to a vehicle seat.

FIG. 1 schematically illustrates a vehicle occupant restraint system100, which incorporates a load-limiting device 102 according to thepresent invention. In FIG. 1 the vehicle occupant restraint system isbelt 104 designed to fit a vehicle passenger. The belt 104 comprises alap belt component 104 a and a shoulder belt component 104 b. The beltalso includes a vertical segment 104 c that is attached to a retractorlocated inside a plastic trim 106. The retractor is coupled to astructural part of a vehicle (e.g. the vehicle floor or the base of thevehicle B pillar). Part of the belt is wound about a spool (not shown)of the retractor 106, which allows controlled payout of the belt as thebelt is being fitted about a vehicle occupant. A buckle 108 is coupledwith an anchor 110 that is secured to a structural part of the vehicle(e.g. the floor of the vehicle). The parts of the belt forming theshoulder component 104 b and the vertical segment 104 c extends througha web guide (or turning loop) 112 that is coupled to a structural partof a vehicle (e.g. the vehicle B-pillar or the roof rail of the vehicle)by the load-limiting device 102 constructed according to the principlesof the present invention. A tongue 115 is connected with the belt 104,and is manually coupled to the buckle 108 by the vehicle occupant. Thetongue 115 separates the belt 104 into the lap and shoulder beltcomponents 104 a, 104 b, but those in the art will recognize that therestraint system can also comprise separate lap belt and shoulder beltcomponents with separate, respective retractors.

During normal vehicle operation, the retractor allows some limitedamount of belt payout, if the vehicle occupant shifts position in thevehicle. However, at the onset of a crash, the retractor locks andprevents further belt payout, to restrain the vehicle occupant duringthe crash. The load-limiting device 102 is designed to absorb kineticenergy of a vehicle occupant as the vehicle occupant loads the beltduring a crash. Specifically, when the vehicle occupant loads the beltduring a crash, force and energy is applied by the vehicle occupant tothe belt, and it is that force and energy that is absorbed by theload-limiting device 102.

Referring to FIGS. 2-6, the load-limiting device 102 includes a housing118 and a deformable member 120 that is moveable relative to the housing118 (i.e. in FIGS. 1A, 2 in the direction depicted by arrow 119). Thedeformable member 120 is connected to the web guide 112 as shown in FIG.1A. Specifically, the housing 118 is configured for connection to theB-pillar or to the vehicle roof rail (e.g. by bolts or screws 121 thatalso couple the housing parts 124, 126 together). The housing and thedeformable member move relative to each other in a predetermined mannerwhen force from the vehicle occupant restraint is applied to thedeformable member 120. The housing 118 has a hardened member, such as ahardened ball 122 (FIGS. 3, 5, 6), formed of a material which is harderthan the deformable member 120. The hardened member is positioned toengage and deform the deformable member as the deformable member isbeing moved relative to the housing

The deformable member 120 preferably comprises an oblong metal strip andthe housing 118 comprises a pair of interfitting housing components 124,126 (FIGS. 3, 5, 6) which define an opening (or slot or groove) 128(FIGS. 2, 6) through which the metal strip 120 is pulled. The hardenedmember 122 may include one or more stems 125 (two stems are illustratedin FIGS. 5 and 6), which fit into mating holes 127 in the housingcomponents 24, 26. Thus, the hardened member 122 is (i) supported by thehousing components 124, 126, (ii) located in the opening 128 and (iii)positioned to engage and deform the metal strip 120 as the metal stripis being pulled through the opening 128 in the housing. Thisrelationship is more clearly shown in FIGS. 3, 5 and 6.

The strip 120 has a first end 130 that is connected to the web guide 112of the vehicle occupant restraint and a spaced second end 132. Thesecond end 132 includes stop member 134 which extends away from thestrip, and limits the effective range of operation of the load limitingmetal strip, as described more fully below. A portion of the strip 120between the first and second ends 130, 132 is configured to be deformed(e.g. plastically deformed) in a predetermined manner when the strip ispulled through the opening 128 in the housing 118 and engaged by thehardened ball 122.

The configuration of the deformable strip 120 can be designed so thatthe deformable strip will deform in a predetermined manner under forcesapplied to the load-limiting device 102 during a crash. For example,according to one embodiment, which is illustrated in FIGS. 2-7, thedeformable strip 120 is configured to deform in a predetermineddigressive force manner as the deformable member is being moved relativeto the housing 118. As used herein and in the claims “digressive forcemanner” means that the force rises quickly and then declines graduallyas force is applied to the vehicle occupant through the restraint. Inanother embodiment, illustrated in FIGS. 8-10, the deformable strip 120is configured to deform in a predetermined relatively constant forcemanner as the deformable strip is being moved relative to the housing118.

In yet another embodiment, illustrated in FIGS. 11 and 12, thedeformable 120 is configured to deform in a predetermined progressiveforce manner as the deformable strip is being moved relative to thehousing 118. As used herein and in the claims “progressive force manner”means that the force initially rises quickly, and then increases moregradually as force is applied to the vehicle occupant through therestraint.

In yet another embodiment, illustrated in FIGS. 13 and 14, thedeformable strip is configured to deform in a digressive step manner asthe deformable strip is being moved relative to the housing 118. As usedherein and in the claims “digressive step manner” means that the forceraises quickly and then has a relatively constant force responsefollowed by a gradually declining force response as force is applied tothe vehicle occupant through the restraint.

As used herein and in the claims reference to the deformable strip 120deforming in a predetermined manner is intended to mean that theforce/displacement curve representing the way the restraint systemresponds (and dissipates forces) when a vehicle occupant loads therestraint system has a predetermined form. In the description of theembodiments that follow, the force/displacement curves are intended toillustrate generally the force/displacement relationships when a vehicleoccupant loads the restraint system, but are not intended to representactual data.

In the embodiment of FIGS. 2-7, the deformable strip 120 is configuredto deform in a predetermined digressive force manner (see FIG. 5) as thestrip is being pulled through the housing 118. As used herein and in theclaims “digressive force manner” means that the force rises quickly, andthen declines gradually as the vehicle occupant loads the restraintsystem. To provide such a digressive force deformation, the strip 120has a longitudinally extending, triangular central opening 136 (FIG. 4),which has a narrower end 138 near the first connection 130, so that thehardened ball 122 engages the narrower end 138 earlier as the balldeforms the strip. The central opening 136 progressively widens as thestrip is pulled through the opening 128 in the housing, so that the ballencounters decreasing resistance to deformation as the strip 118 ispulled through the opening 128, thereby producing the digressive forcecharacteristics of FIG. 7 on the vehicle occupant restraint. Also, itshould be noted that as the strip is pulled through the opening 128, thestems 125 (which are located in the holes 127 in the housing components124, 126) hold the hardened member 122 in place, thereby causing thestrip 120 to be deformed by the hardened member as the strip 120 ispulled through the opening 128 in the housing.

While the hardened member 122 disclosed is a ball with stems 125 thatfit into holes 127 in the housing components 124, 126, the dimensions ofthe ball and the housing components may be controlled tightly enoughthat the stems and holes may not be necessary to hold the hardenedmember in place in the housing. Either housing component may have ahardened portion formed in one piece with that housing component andconfigured to engage and deform the strip 120 as the strip is pulledthrough the housing.

In the embodiment of FIGS. 8 and 10, the deformable strip 120 isconfigured to deform in a predetermined relatively constant force manner(see FIG. 10) as the strip is being pulled through the housing 118. Toprovide such a relatively constant force deformation, the strip 120 hasa longitudinally extending rectangular shaped central opening 140 thathas a generally constant width 142. Thus, the hardened ball 122encounters a generally constant resistance to deformation as the strip120 is pulled through the housing 118, thereby producing the relativelyconstant force/displacement characteristics of FIG. 10 on the vehicleoccupant restraint.

In addition, in the embodiment shown in FIG. 9, the deformable strip 120is also configured to deform with relatively constant force/displacementdeformation characteristics. Specifically, the strip either has nolongitudinal extending central opening, that is, it is a solid piece ofmetal through its operating length), or it has a longitudinalperforation 144 along its centerline. If the strip has no centralopening, and the hardened ball 122 deforms the strip 120 in a mannerthat is relatively constant along the perforation, so that thedeformation of the strip should deform with relatively constantforce/displacement deformation characteristics. If the strip has alongitudinal perforation 144 along its centerline, the perforation 144will provide the strip 120 with some central weakness, allowing thedeformation of the strip to be initiated easier than it would withoutthe perforation, but once initiated the deformation of the strip will berelatively constant along the perforation, and the strip will deformwith relatively constant force/displacement deformation characteristicsas shown in FIG. 10.

In the embodiment illustrated in FIGS. 11 and 12, the deformable strip120 is configured to deform with predetermined progressiveforce/displacement characteristics, as shown in FIG. 12, as the strip120 is being pulled through the housing 118. As used herein and in theclaims “progressive force/displacement characteristics” means that theforce initially rises quickly, and then gradually increases as thevehicle occupant loads the restraint. Specifically, the strip has alongitudinally extending central opening 150 that is triangularlyshaped, with a wider leading end 152 near the first part 130 of thestrip that is coupled to the vehicle occupant restraint. With thisconfiguration, the initial deformation of the strip requires lessenergy, on account of the wider leading end 152 of the central opening150. However, as the deformation of the strip progresses, more energy isrequired, because the central opening progressively narrows as the stripis pulled through the housing 118. Hence, the deformation of the striprequires progressively more energy, and the deformation characteristicswill conform to the progressive force/displacement deformationcharacteristics of FIG. 12.

In the embodiment of FIGS. 13 and 14, the deformable strip 120 isconfigured to deform in a digressive step manner (FIG. 14) as the stripis being pulled through the housing. As used herein and in the claims“digressive step manner” means that the force/displacementcharacteristic raises quickly, and then has a relatively constantforce/displacement response followed by a gradually decliningforce/displacement response as the vehicle occupant loads the restraint.Specifically, the strip 120 has a longitudinally extending centralopening 160 with a relatively narrow portion 162 nearest the firstcoupling 130, and which maintains that narrow width for a predeterminedlongitudinal extent and then progressively widens as it extendslongitudinally away from the relatively narrow portion 162. Thus, thestrip requires a relatively high amount of energy to deform it over apredetermined length (i.e. the length of the narrow portion 162) andachieves a relatively constant force/displacement response, and thengradually less energy to deform it because it then progressively widensas it continues to be pulled through the housing 118, thereby providingthe digressive step force/displacement deformation characteristics ofFIG. 14.

In each of the foregoing embodiments, load-limiting device can beselectively designed (i.e. “tuned”) for a particular type ofperformance. For example, the deformation characteristics of theload-limiting device are at least partially determined by theconfiguration of the central portion of the strip 120, i.e. theconfiguration of the central openings 136, 140, 150, 150, theperforations 144, or the absence of a central opening. In addition,there are other features of the load-limiting device that allow theload-limiting device to be selectively designed for a particular type ofperformance. Those features include the modulus of elasticity of thedeformable strip, the thickness of the deformable strip, the diameter ofthe ball (or other geometry of the deforming member), other geometriccharacteristics of the deformable member, and the materials of thedeforming member and the deformable member.

In addition, in all of the foregoing embodiments, the second portion 132of the deformable strip 120 has the stop 134 that will engage thehousing 118 at the end of travel of the strip relative to the housing. Astop member 134 can be attached to the second end of the strip can formthe stop 134, for example, or the stop can be formed in one piece withthe strip. The stop 134 is configured so that if strip 120 is pulledthrough the housing to a point where the stop 134 engages the housing,the deformation of the strip will cease, and the load on the vehicleoccupant will rise dramatically. However, by that time, theload-limiting device will have basically done its job, and other aspectsof the restraint system (e.g. a vehicle air bag) will be primarilyresponsible for absorbing the energy of a vehicle occupant during thecrash. Thus, the stop 134 is not part of the parameters that determinesthe deformation characteristics of the strip, as will be readilyappreciated by those in the art.

In determining which type of deformation characteristics may best suit aload limiting device for a vehicle occupant restraint, basically thecrash characteristics of the vehicle and the environment in which thevehicle occupant restraint is expected to function drive suchdeterminations. As the load-limiting device performs its function, itconverts the kinetic energy of the vehicle occupant into the “work”required to deform the load-limiting device. The more energy absorbed bythe deformation of the vehicle occupant restraint, the less energy andforce that is applied to the vehicle occupant by the restraint systemduring a crash. The earlier in the crash the load limiting device beginstaking up the kinetic energy of the vehicle occupant, the more time thevehicle occupant restraint has to transfer energy into the vehicle andthe transfer of such energy can be at a lower rate and consequently atlower peak loads. Thus, it will more often be desirable for theload-limiting device to have digressive (FIGS. 2-7) or digressive step(FIGS. 13, 14) deformation characteristics, to provide the highest takeup of vehicle occupant kinetic energy early in the crash.

It should be noted that while in the illustrated embodiment the housing118 is fixed to a structural part of the vehicle, and one end of thestrip 120 is coupled to the vehicle occupant restraint and is pulledthrough the housing 118, that configuration could be reversed, i.e., oneend of the strip 120 could be fixed to the structural part of thevehicle, and the housing 118 could be coupled to the vehicle occupantrestraint. In either configuration, the strip is pulled through thehousing, which results in the deformation of the strip, with the typesof deformation characteristics described above.

It should be noted that it is currently contemplated that the deformablestrip would be formed of 1010 to 1020 mild steel, but other types ofrelatively mild, deformable material will occur to those in the art. Inaddition, it is currently contemplated that the hardened member may beformed, e.g. of A2 tool steel hardened to Rockwell C of 65, or by amilder steel that is chrome plated to the appropriate hardness. It isalso recognized that other types of materials for forming the hardenedmember will occur to those in the art.

The foregoing disclosure provides a load-limiting device for a vehicleoccupant restraint that is designed to dissipate forces applied to thevehicle occupant in a predetermined manner during a crash, to absorbenergy applied to a vehicle occupant during a crash. Moreover, thedesign of the load-limiting device of the present invention providessignificant flexibility in designing the predetermined manner in whichthe load-limiting device dissipates forces during a crash, therebyproviding flexibility in how energy of a vehicle occupant is absorbedduring a crash. With the foregoing disclosure in mind, there will beother modifications and developments that will be apparent to those inthe art.

1. An apparatus comprising a load limiting device which serves as aconnection between a vehicle safety restraint and an anchor point, theload limiting device comprising a housing and a deformable member, atleast one of which is configured for connection to a vehicle safetyrestraint and the other of which is configured for connection to theanchor point, the housing and the deformable member being moveablerelative to each other in a predetermined manner when force is appliedto one or the other of the housing and the deformable member, and thehousing having a hardened member which is harder than the deformablemember, the hardened member positioned to engage and deform thedeformable member as the deformable member moves relative to thehousing.
 2. The apparatus of claim 1 wherein the housing comprises apair of housing components which define an opening through which thedeformable member is pulled and wherein the hardened member is (i)supported by the housing components, (ii) located in the opening in thehousing and (iii) positioned to engage and deform the deformable memberas the deformable member is being pulled through the opening in thehousing.
 3. The apparatus of claim 2, wherein the deformable membercomprises a strip having a first portion configured for connection to acomponent of safety restraint system and a second portion having a stop;the strip having a central portion located between the first and secondportions that is configured to be deformed in a predetermined mannerwhen the strip is pulled through the housing and engaged by the hardenedmember.
 4. The apparatus of claim 3, wherein the strip is formed of mildsteel, and the hardened member comprises a ball made of hardened steel.5. The apparatus of claim 3 wherein the strip is configured to deform ina digressive force manner as the strip is being pulled through thehousing.
 6. The apparatus of claim 5, wherein the strip has a centralopening that progressively widens as the strip is pulled through thehousing and engaged by the hardened member.
 7. The apparatus of claim 3wherein the strip is configured to deform in a relatively constant forcemanner as the strip is being pulled through the housing.
 8. Theapparatus of claim 7, wherein the strip has a central opening that has arelatively constant width, to enable the strip to deform in a relativelyconstant force manner, as the strip is pulled through the housing andengaged by the hardened member.
 9. The apparatus of claim 7, wherein thecentral portion of the strip has a perforation, that facilitatesinitiation of deformation of the strip and enables the strip to deformin a relatively constant force manner, as the strip is pulled throughthe housing and engaged by the hardened member.
 10. The apparatus ofclaim 3, wherein the strip is configured to deform in a progressiveforce manner as the strip is being pulled through the housing.
 11. Theapparatus of claim 10, wherein the strip has a central opening thatprogressively narrows as the strip is pulled through the housing andengaged by the hardened member.
 12. The apparatus of claim 3, whereinthe strip is configured to deform in a digressive step manner as thestrip is being pulled through the housing.
 13. The apparatus of claim12, wherein the strip has a central opening that is initially constantin width and then progressively widens as the strip is pulled throughthe housing and engaged by the hardened member.
 14. The apparatus ofclaim 1, wherein the deformable member is configured to deform in adigressive force manner as the deformable member is being moved relativeto the housing.
 15. The apparatus of claim 1, wherein the deformablemember is configured to deform in a relatively constant force manner asthe deformable member is being moved relative to the housing.
 16. Theapparatus of claim 1, wherein the deformable member is configured todeform in a progressive force manner as the deformable member is beingmoved relative to the housing.
 17. The apparatus of claim 1, wherein thedeformable member is configured to deform in a digressive step manner asthe deformable member is being moved relative to the housing.